So so glad that this proposal was brought up, and I really really hope that it doesn't end as a dead proposal. I think for any game, or even for any service with user-submitted content, it's much more healthy for it to keep the redundant content or the content bloat at bay, right?
Well, I think that depends on what we want osu! to become in the long run. I always advocate for having a permissive ranking criteria that allows many things for it to get through, in order to have more variety in the ranked section... but at the same time, since many people do like to map in this sort of way, implementing something like this would be the exact opposite of being permissive, rather barring maps from getting to the ranked section. So, pros and cons, yeah.
Looking at the two perspectives:
If we were to continue with the current system, where mappers go for pp/attention most of all, it's not necessarily a bad thing. As people have said, there's people right now that do enjoy the current state of things despite them being 'bad', and I think pp mapping, or mapping for attention will never truly disappear (think of them like the clickbaity videos in YouTube... they work, that's why they exist). Continuing like this sets a standard on what is 'common' ranked mapping, thus making maps that are different really stand out, plus everyone gets a true and fair chance on getting to the ranked section. As a player, once you happen to stumble upon a mapper that maps this kind of way, you rather just know that you want to stay away from his/her maps - and the issue of the players feeling pressured to play these types of maps to stay in the top rankings, that may only be related with the pp system directly, and not so much with the mapping it has influenced, at least from my point of view.
So the current state of things, I see it as an even ground for everyone (or at least, as even as it can get) but... for the game as a whole, it does not give it a good image. It may make players think that this is all osu! is about and make them quickly quit the game, and sure enough, in an ideal world you wouldn't need to dig too deep to find something interesting out there. We wouldn't be able to pride ourselves in belonging to a community where only the highest standard is held - since we know so many things pass through without too much effort, or that there are many other interests for mappers than just trying to bring something interesting to the table. We would know as a community that there's too much content bloat, and aren't really doing anything to change that. But just maybe that can be countered with the beatmap spotlights, or with the staff trying to bring more attention to maps that really deserve it in some other way, I'm not sure if that's as effective though.
Now, if something like this were implemented...
Hopes are that, pp maps would be more limited. Less pp difficulties in the same set, or even less pp sets entirely. No more grinding the same songs over an over with similar mapping ideas - we know there's no content bloat happening, and that you can find something new and unique on each map. Even though there would be lots of backlash from mappers, the game as a whole would become more interesting, even if it's forcing the mappers to change their habits/way of mapping. I don't think it would make the game instantly better, as the first sets of a song, or first difficulties of a set, would still be pp and still get more plays (and I guess that's why this is called a 'band-aid' solution?) but, I think it would be a great first step as other mappers would need to forcefully find other, more interesting ways to represent a song in a map.
If I put myself in the shoes of someone who made a pp map and tried to get it ranked as a GD, but was told later that it was removed due to ranking criteria standards, and would not be able to get it through with significant changes, it would make me really mad, since I had spent so much time and effort mapping that (also because I would not be provided the opportunity to push it through, just because someone else beat me to it). Despite my rage though, for the game it would also make perfect sense since, if the map I created is extremely similar to an already ranked one, or a difficulty of the same set, what are you really going to provide to the ranked section? It would be time to ask myself, am I really bringing anything interesting or anything new to the table? That's why I think, if we were going this way, barring sets or difficulties from ranking is completely valid, as we want the game to provide something different and unique for everyone - as painful as it would be to the mapper putting their effort and time on the map, just telling them "sorry, you can't get in, try again - the game requires something different now".
I mean, we kinda know already that with any sort of change, people are going to get mad. But if it's for making the game better as a whole (better in this context meaning to provide more variety), then I think we should go ahead and embrace ourselves for the outrage this is going to cause. Myself personally, I'm all for a proposal like this.
tl;dr - I think this most of all depends if we all, as a community, want to start enforcing subjective quality standards again, with the mapper outrage it's going to ensue, Loctav-era style again. Do we want to keep mappers happy, or do we want to make the game more varied with its maps?
As I see it right now, the community is divided and has been for some time. If we can all get on the same page though, I'm on board.
(Sorry if I actually failed to tackle the currently discussed points or digressed a little bit, just felt like that's a strong point that should be clarified first. There is another thing I wanted to say, but I'll leave it like this for now I guess).